The free and portable Radical Image Optimization Tool (RIOT) has been an app I’ve recommended for a few years now (I think I’ve been using it since about 2008). As the name suggests it focuses on doing one thing, and doing it well: optimizing images. It can compress, resize, adjust, and convert your images in a way that leaves you in control of the end result.

The thing I like the most about riot is how easily I can manipulate multiple photos in just a few clicks. Thanks to the “batch” button on the toolbar I can select an entire folder of images that I want to resize and/or compress, and the speed at which it can process the images is rather incredible. This is great for emailing off a slew of photos when you’re concerned about the attachment size.

Most of the time I use RIOT for batch optimizations, but this regularly-updated app is equipped with all kinds of other features:

Open many image types including rare/scientific types

Save and optimize JPEG, GIF and PNG with a simple, clean user interface

Works in dual view: (original – optimized image) or single view (optimized image).

Automatic preview of resulting image

In-place compare function (alternativelly display the original image over the optimized image to notice small pixel changes)